Spinal fixation systems may be used in surgery to align, adjust and/or fix portions of the spinal column, i.e., vertebrae, in a desired spatial relationship relative to each other. Many spinal fixation systems employ a spinal rod for supporting the spine and for properly positioning components of the spine for various treatment purposes. Vertebral anchors, comprising pins, bolts, screws, and hooks, engage the vertebrae and connect the supporting rod to different vertebrae. The size, length and shape of the cylindrical rod depend on the size, number and position of the vertebrae to be held in a desired spatial relationship relative to each other by the apparatus.
During spinal surgery, a surgeon first exposes the spine posterior and attaches the vertebral anchors to selected vertebrae of the spine. The surgeon then inserts a properly shaped spinal rod into rod-receiving portions of the vertebral anchors to connect the selected vertebrae, thereby fixing the relative positions of the vertebrae. Generally, a controlled mechanical force is required to bring together the spinal rod and a spinal implant, such as the vertebral anchors, in a convenient manner. After insertion, a surgeon must insert a locking mechanism, such as a set screw, into the vertebral anchor to lock the spinal rod to the implant after the force for inserting the rod is removed.
There are currently various devices designed and used for reduction of a spinal rod into a vertebral anchor or other spinal implant, which have significant drawbacks. Drawbacks include difficultly generating the amount of force required to insert a spinal rod into implant, difficulty of aligning the rod to the rod-receiving portion of an implant and the lack of direct tactile feedback to the hand of the surgeon. In addition, many devices for coupling a spinal rod and a vertebral anchor include many complex parts and can be difficult or complex to operate.
For example, U.S. Pat. No. 6,660,006 is directed to a rod reduction device including a body releasably attached to an orthopedic device, a pusher member and a trigger slidably coupling the pusher member to the body. The rod reduction device described in U.S. Pat. No. 6,660,006 includes a channel for inserting a fastener extending through the entire body of the instrument. The inter-body channel increases the size and complexity of the rod reduction device. In addition, the location of the channel within the body blocks the channel from view and inhibits access to the channel.